hej all,i'm trying to build a circuit with LOUD sound, but small form factor -- so i've been looking towards mobile phone speakers -- the ones that play music quite full-range and super loud. see here for example: http://httpwwwglobalsourcesmguisound.manufacturer.globalsources.com/si/6008820642893/pdtl/Micro-speaker/1007463385/Speaker.htmi've been trying to power this little bugger with a normal op-amp circuit, but that doesn't seem to give it juice enough (audio is barely hearable) -- can someone help me out with a circuit?or, perhaps, a powerful audio op amp?best,/j

i just tried setting this up, and the result is that the speaker goes to one extreme or the other, depending on the setting of the variable resistor...

[EDIT] for mem: took a pic of my setup... could you verify i am doing this right here? (green and white wire was only shorted when taking the picture, not when testing the circuit) transistor is TIP120 -- audio signal is coming through the phono wire. 5V through red wire. [/EDIT]

this makes me think: will this also work with audio output from a DAC? - so not only on/off signals, but 12 bit waveforms running to the base of the transistor...?thanks,/j

@mem: it's a MCP4921 -- i have basically copied the schematic of the arduino pocket piano for my sound generation circuit: http://www.critterandguitari.com/home/store/pocketPiano/PocketPianoSchematic.gifi have sound coming out of my output -- if i insert it to a mixer i get a nice signal, so i don't see any need for the sketch here. (its big and messy) --- but, again, basically its the same as the pocket piano project: http://www.critterandguitari.com/home/store/pocketPiano/HelloSineTone.zip

@AWOL: sounds perfect! can you give me a serial number of an amplifier like that?

That clarifies things, you didn't mention the D/A in your earlier posts so my comments assumed that you were driving the output from an arduino pin.

Any audio amp for driving a speaker should work. You can make one using your TIP120 and a couple of 100k resistors using the information here: http://sci-toys.com/scitoys/scitoys/computers/solderless/amplifier.html